Intent to Ship: WebAssembly Garbage Collection (WasmGC)

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Emanuel Ziegler

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Sep 12, 2023, 3:31:04 PM9/12/23
to blink-dev, Jakob Kummerow, Adam Klein, Lutz Vahl

Dear API owners,


Following the continued experiment for Garbage Collected WebAssembly (WasmGC), we plan to ship the feature in M119 after the positive vote to phase 4 by the WebAssembly Community Group today.


The feature has shown very good performance with reasonable compromises. The findings from the origin trial are summarized in a public document.


This feature is tied to the Function References proposal which is a de-facto part of WasmGC (no current use outside of the proposal, hard requirement for WasmGC) and only listed as a separate proposal for historic reasons. The Function References proposal has therefore also been voted to phase 4 on the same day as WasmGC.


We plan to launch the feature in the following manner:

  1. End the current origin trial with M118 as its last milestone

  2. Refactor the binary instruction representation to match the final spec (incompatible change)

  3. Ship the feature with M119


Our data from the trial has shown that there is a need for fast string interoperability with JS that this proposal does not address. We plan to launch a new experiment investigating different approaches to this problem (see separate I2E mail).



Contact emails

ad...@chromium.orgjkum...@chromium.org

Explainer

https://github.com/WebAssembly/gc/blob/master/proposals/gc/Overview.md
https://github.com/WebAssembly/function-references/blob/main/proposals/function-references/Overview.md

Specification

https://github.com/WebAssembly/gc/tree/main/proposals/gc

Summary

The GC proposal adds efficient support for high-level managed languages to WebAssembly, via struct and array types that enable language compilers targeting Wasm to integrate with a garbage collector in the host VM. In Chrome, enabling this feature implies enabling Typed Function References, which allow function references to be stored in the aforementioned structs and arrays.



Blink component

Blink>JavaScript>WebAssembly

Search tags

wasmwebassemblygcmanaged objectswasmgc

TAG review

https://github.com/w3ctag/design-reviews/issues/814

TAG review status

Issues addressed

Risks



Interoperability and Compatibility



Gecko: Positive

WebKit: No signal

Web developers: Positive Google Sheets, which is currently compiling Java to JavaScript, is experimenting with using WasmGC to speed up their calculation engine. JetBrains is working on a Kotlin -> WasmGC compiler. Dart is working on a Dart -> WasmGC compiler, in collaboration with Flutter.

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?



Debuggability



Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

No

Is this feature fully tested by web-platform-tests?

No

Flag name on chrome://flags



Finch feature name

None

Non-finch justification

The feature does not enable any functionality without the module being explicitly compiled for that feature. We therefore chose to use an origin trial to evaluate its suitability and stability. This allowed websites that want to try this feature to opt in and do their own A/B comparisons.



Requires code in //chrome?

False

Tracking bug

https://bugs.chromium.org/p/v8/issues/detail?id=7748

Launch bug

https://launch.corp.google.com/launch/4231622

Estimated milestones

OriginTrial desktop last120
OriginTrial desktop first112
OriginTrial Android last120
OriginTrial Android first112


Anticipated spec changes

Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).



Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6062715726462976

Links to previous Intent discussions

Intent to Experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/HDbvHCVFSW0
Intent to Extend Experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/7F_daEqGQAY
Intent to Ship: https://groups.google.com/a/chromium.org/g/blink-dev/c/7F_daEqGQAY


This intent message was generated by Chrome Platform Status.

Mike Taylor

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Sep 15, 2023, 4:26:25 PM9/15/23
to Emanuel Ziegler, blink-dev, Jakob Kummerow, Adam Klein, Lutz Vahl

On 9/12/23 9:22 PM, 'Emanuel Ziegler' via blink-dev wrote:

Dear API owners,


Following the continued experiment for Garbage Collected WebAssembly (WasmGC), we plan to ship the feature in M119 after the positive vote to phase 4 by the WebAssembly Community Group today.


The feature has shown very good performance with reasonable compromises. The findings from the origin trial are summarized in a public document.


This feature is tied to the Function References proposal which is a de-facto part of WasmGC (no current use outside of the proposal, hard requirement for WasmGC) and only listed as a separate proposal for historic reasons. The Function References proposal has therefore also been voted to phase 4 on the same day as WasmGC.


We plan to launch the feature in the following manner:

  1. End the current origin trial with M118 as its last milestone

  2. Refactor the binary instruction representation to match the final spec (incompatible change)

  3. Ship the feature with M119

This plan sounds good. Thx.


Our data from the trial has shown that there is a need for fast string interoperability with JS that this proposal does not address. We plan to launch a new experiment investigating different approaches to this problem (see separate I2E mail).



Contact emails

ad...@chromium.orgjkum...@chromium.org

Explainer

https://github.com/WebAssembly/gc/blob/master/proposals/gc/Overview.md
https://github.com/WebAssembly/function-references/blob/main/proposals/function-references/Overview.md

Specification

https://github.com/WebAssembly/gc/tree/main/proposals/gc

Summary

The GC proposal adds efficient support for high-level managed languages to WebAssembly, via struct and array types that enable language compilers targeting Wasm to integrate with a garbage collector in the host VM. In Chrome, enabling this feature implies enabling Typed Function References, which allow function references to be stored in the aforementioned structs and arrays.



Blink component

Blink>JavaScript>WebAssembly

Search tags

wasmwebassemblygcmanaged objectswasmgc

TAG review

https://github.com/w3ctag/design-reviews/issues/814

TAG review status

Issues addressed

Risks



Interoperability and Compatibility



Gecko: Positive

WebKit: No signal


Web developers: Positive Google Sheets, which is currently compiling Java to JavaScript, is experimenting with using WasmGC to speed up their calculation engine. JetBrains is working on a Kotlin -> WasmGC compiler. Dart is working on a Dart -> WasmGC compiler, in collaboration with Flutter.

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?



Debuggability

Can you say more about this?


Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

No
Can you say more about this?


Is this feature fully tested by web-platform-tests?

No
In this case, is this new feature covered by existing wasm test suites?


Flag name on chrome://flags



Finch feature name

None
Presumably this is behind a feature, if an Origin Trial occured, right?
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Adam Klein

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Sep 15, 2023, 5:13:31 PM9/15/23
to Mike Taylor, Emanuel Ziegler, blink-dev, Jakob Kummerow, Lutz Vahl
Thanks for the reply, Mike. I'm going to fill in some of this to avoid blocking over the weekend.
Since this is a Phase 4 proposal within the Wasm CG, the process does not normally require a signal, as documented in https://bit.ly/blink-signals. Are you requesting an exception-to-the-exception here?

FWIW an implementation is well underway, tracked at https://bugs.webkit.org/show_bug.cgi?id=247394.
 


Web developers: Positive Google Sheets, which is currently compiling Java to JavaScript, is experimenting with using WasmGC to speed up their calculation engine. JetBrains is working on a Kotlin -> WasmGC compiler. Dart is working on a Dart -> WasmGC compiler, in collaboration with Flutter.

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?



Debuggability

Can you say more about this?

Copying what I wrote in the original Intent to Experiment:

Wasm GC is debuggable using devtools, including sourcemap support & profiling. We expect support to improve over time as toolchain implementers work on improving developer experience, analogous to what we currently have with DWARF-based C++ debugging in Emscripten + the Devtools DWARF extension.
 

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

No
Can you say more about this?

This was a data entry error, the feature is supported on all Blink platforms.

Is this feature fully tested by web-platform-tests?

No
In this case, is this new feature covered by existing wasm test suites?

Yes, like all Wasm proposals it's covered by spec tests that are part of the proposal.

Flag name on chrome://flags



Finch feature name

None
Presumably this is behind a feature, if an Origin Trial occured, right?

Yes. The Blink runtime enabled feature is called "WebAssemblyGC".

Yoav Weiss

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Sep 16, 2023, 1:40:03 AM9/16/23
to Adam Klein, Mike Taylor, Emanuel Ziegler, blink-dev, Jakob Kummerow, Lutz Vahl
LGTM1

I don't think an exception to the exception is needed here.
 

Mike Taylor

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Sep 16, 2023, 10:24:15 AM9/16/23
to Yoav Weiss, Adam Klein, Emanuel Ziegler, blink-dev, Jakob Kummerow, Lutz Vahl

LGTM2 - thanks Adam.

Nah, that's just me forgetting the exceptions. :) Thanks for reminding me.

Chris Harrelson

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Sep 19, 2023, 12:07:14 PM9/19/23
to Mike Taylor, Yoav Weiss, Adam Klein, Emanuel Ziegler, blink-dev, Jakob Kummerow, Lutz Vahl

Thomas Steiner

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Sep 19, 2023, 1:04:43 PM9/19/23
to Chris Harrelson, Mike Taylor, Yoav Weiss, Adam Klein, Emanuel Ziegler, blink-dev, Jakob Kummerow, Lutz Vahl
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